In a typical radio communications network, wireless terminals, also known as mobile stations and/or user equipments (UEs), communicate via a Radio Access Network (RAN) to one or more core networks. The radio access network covers a geographical area which is divided into cell areas, with each cell area being served by a base station, e.g., a radio base station (RBS), which in some networks may also be called, for example, a “NodeB” or “eNodeB”. A cell is a geographical area where radio coverage is provided by the radio base station at a base station site or an antenna site in case the antenna and the radio base station are not collocated. Each cell is identified by an identity within the local radio area, which is broadcast in the cell. Another identity identifying the cell uniquely in the whole mobile network is also broadcasted in the cell. One base station may have one or more cells. A cell may be downlink and/or uplink cell. The base stations communicate over the air interface operating on radio frequencies with the user equipments within range of the base stations.
A Universal Mobile Telecommunications System (UMTS) is a third generation mobile communication system, which evolved from the second generation (2G) Global System for Mobile Communications (GSM). The UMTS terrestrial radio access network (UTRAN) is essentially a RAN using wideband code division multiple access (WCDMA) and/or High Speed Packet Access (HSPA) for user equipments. In a forum known as the Third Generation Partnership Project (3GPP), telecommunications suppliers propose and agree upon standards for third generation networks and UTRAN specifically, and investigate enhanced data rate and radio capacity. In some versions of the RAN as e.g. in UMTS, several base stations may be connected, e.g., by landlines or microwave, to a controller node, such as a radio network controller (RNC) or a base station controller (BSC), which supervises and coordinates various activities of the plural base stations connected thereto. The RNCs are typically connected to one or more core networks.
Specifications for the Evolved Packet System (EPS) have been completed within the 3rd Generation Partnership Project (3GPP) and this work continues in the coming 3GPP releases. The EPS comprises the Evolved Universal Terrestrial Radio Access Network (E-UTRAN), also known as the Long Term Evolution (LTE) radio access, and the Evolved Packet Core (EPC), also known as System Architecture Evolution (SAE) core network. E-UTRAN/LTE is a variant of a 3GPP radio access technology wherein the radio base station nodes are directly connected to the EPC core network rather than to RNCs. In general, in E-UTRAN/LTE the functions of a RNC are distributed between the radio base stations nodes, e.g. eNodeBs in LTE, and the core network. As such, the Radio Access Network (RAN) of an EPS has an essentially “flat” architecture comprising radio base station nodes without reporting to RNCs.
UL Transmissions in LTE
In the current LTE standard, UL signal transmissions comprise uplink physical channel transmissions and uplink physical signal transmissions. A physical channel typically corresponds to a set of resource elements carrying information originating from higher layers. Example uplink physical channels: Physical Uplink Shared Channel (PUSCH), Physical Uplink Control Channel (PUCCH), Physical Random Access Channel (PRACH). An uplink physical signal is used by the physical layer but typically does not carry information originating from higher layers. Example uplink physical signals are reference signal, of which there currently two types defined in LTE: Demodulation Reference Signal (DMRS) associated with transmission of PUSCH or PUCCH, and Sounding reference signal (SRS), not associated with transmission of PUSCH or PUCCH.
Dynamically Scheduled UL Transmissions
In the LTE uplink, E-UTRAN can dynamically allocate resources to user equipments at each Transmission Time Interval (TTI) with a 1 ms granularity via the Cell Radio Network Temporary Identifier (C-RNTI) on Physical Downlink Control Channel(s) (PDCCH). A user equipment always monitors the PDCCH(s) in order to find possible allocation for uplink transmission when its downlink reception is enabled, activity governed by Discontinuous Reception (DRX) when configured. When carrier aggregation is configured, the same C-RNTI applies to all serving cells.
A user equipment receives in subframe an UL grant and transmits in the UL in subframe n+k with k=4 for Frequency-Division Duplexing (FDD); in Time-Division Duplexing (TDD) k is more complicated and specified via table 8-2 in 36.213 v. 11.0.0. The UL grant contains parameters that are needed to describe the UL transmission so that a receiver is capable of decoding the transmission. Among others, the parameters contained in UL grant are: frequency hopping flag, resource block assignment, power control command for PUSCH, SRS request, resource allocation type, e.g., multi-cluster transmissions, modulation and coding scheme, cyclic shift and orthogonal cover code for DMRS. For a complete list of parameters, see Section 5.3.3.1.1 in TS 36.312 v.11.0.0. An UL grant for a multi-antenna transmission contains in addition Modulation and Coding Scheme (MCS) for a second transport block and precoding information, see Section 5.3.3.1.8 in TS 36.212, v. 11.0.0.
In LTE, UL grants are transmitted in Downlink Control Information (DCI) formats 0, for single-antenna transmissions, and 4 for multi-antenna transmissions.
UL grants can either be transmitted on PDCCH or on enhanced PDCCH (ePDCCH). ePDCCH is a new control channel that is introduced in Rel-11. ePDCCH does not rely on cell-specific reference signals but on UE specific reference signals. Advantages of ePDCCH over PDCCH are among other improved interference mitigation and beamforming possibilities.
Semi-persistent UL Transmissions
For small UL transmissions—a typical example is Voice over IP (VoIP)—the PDCCH overhead for UL grants required for each UL transmission can become rather large. Therefore, E-UTRAN can allocate a semi-persistent uplink resource for the first Hybrid Automatic Repeat Request (HARQ) transmissions and potentially retransmissions to user equipments:                Radio Resource Control (RRC) defines the periodicity, any of: 10, 20, 32, 40, 64, 80, 128, 160, 320, or 640 subframes, of the semi-persistent transmissions,        PDCCH indicates whether the uplink grant is a semi-persistent one i.e. whether it can be implicitly reused in the following TTIs according to the periodicity defined by RRC.        
Hence, with a special DCI format 0 transmission, Semi-Persistent Scheduling (SPS) activation, semi-persistent scheduling is started once it has been configured. Which resources to use in the first semi-persistent transmission follows from the SPS activation grant. Resources used for subsequent semi-persistent transmissions are the same as in the original transmission, except subframe, subframes for subsequent transmissions are derived from the first transmission time together with the RRC configured periodicity.
The semi-persistent UL scheduling configuration provided via RRC may also comprise power control parameters and a trigger of two-intervals-Semi-Persistent Scheduling in uplink, for TDD only.
In the sub-frames where the user equipment has semi-persistent uplink resource, if the user equipment cannot find its C-RNTI on the PDCCH(s), an uplink transmission according to the semi-persistent allocation that the UE has been assigned in the TTI can be made. For semi-persistent scheduling, semi-persistent scheduling C-RNTI, a special type of C-RNTI, which is provided to the user equipment via RRC together with the SPS information is used as unique identifiers.
Semi-persistent scheduled UL resources become invalid either if an SPS deactivation PDCCH is received or if the UE does not use the semi-persistent scheduled resources a number of times in a row. The number is configured by RRC and can be one of: 2, 3, 4, or 8 subframes.
SPS activation and deactivation messages can be sent both on PDCCH and ePDCCH.
Multi-cluster UL Transmissions
With carrier aggregation, semi-persistent uplink resources can only be configured for the Primary Cell (PCell) and only PDCCH allocations for the PCell can override the semi-persistent allocation.
In carrier aggregation, the user equipment may transmit over multiple Component Carriers (CC), a.k.a. N-times clustered Discrete Fourier Transform Spread—Orthogonal Frequency-Division Multiplexing (DFTS-OFDM); however, the user equipment may also have a multi-cluster transmission, aka in 3GPP UL resource allocation type 1, within a carrier or Component Carrier (CC) and hereby allowing for non-contiguous allocation of scheduled resource blocks, for PUSCH only, and thus giving more scheduling flexibility in frequency domain for UL e.g., enabling more flexible frequency-selective scheduling in UL. The number of clusters is limited to two in LTE in the current specification.
The multi-cluster technique, however, produces a peakier signal, i.e. its associated cubic metric, measure for peakyness, is increased resulting in a larger required power back-off at the user equipment.
FIG. 1 discloses a Multi-cluster UL transmission vs. a multi-carrier transmission. Multi-cluster transmission is configured as Type 1 resource allocation, see e.g. subclause 8.1.2 in TS 36.213 v. 11.0.0. Currently, two resource allocation schemes Type 0, contiguous allocation, and Type 1, multi-cluster allocation, are supported for PDCCH/ePDCCH with uplink DCI format. The use of Type 1 resource allocation is configured via RRC. Even if Type 1 resource allocation is configured, Type 0 resource allocation is always available as fallback solution.
UE Capabilities Associated with Multi-cluster Transmission
The 3GPP standard, sections 4.3.4.13 and 4.3.4.14 in TS 36.306 v.11.0.0, defines the following two UE capabilities associated with multi-cluster transmissions:                multiClusterPUSCH-WithinCC: UE baseband support of multi-cluster PUSCH transmission within a component carrier, this is a band-agnostic capability,        nonContiguousUL-RA-WithinCC-Info: UE RF support of non-contiguous UL resource allocations within a component carrier; this field is signaled per E-UTRA radio frequency band and indicates in which bands the user equipment supports non-contiguous UL resource allocation, the indicators are listed in the same order as in supportedBandListEUTRA.        
The user equipment supporting multi-cluster transmissions should have both capabilities described above.
The two capabilities above are signaled over RRC from the user equipment to the radio base station.
 PhyLayerParameter-v1020 ::=SEQUENCE { twoAntennaPortsForPUCCH-r10ENUMERATED{supported}OPTIONAL, tm9-With-8Tx-FDD-r10ENUMERATED{supported}OPTIONAL, pmi-Disabling-r10ENUMERATED{supported}OPTIONAL, crossCarrierScheduling-r10ENUMERATED{supported}OPTIONAL, simultaneousPUCCH-PUSCH-r10ENUMERATED{supported}OPTIONAL, multiClusterPUSCH-WithinCC-r10ENUMERATED{supported}OPTIONAL, nonContiguousUL-RA-WithinCC-List-r10 NonContiguousUL-RA-WithinCC-List-r10OPTIONAL} NonContiguousUL-RA-WithinCC-List-r10 ::=SEQUENCE(SIZE (1..maxBands)) OF NonContiguousUL-RA-WithinCC-r10 NonContiguousUL-RA-WithinCC-r10 ::=SEQUENCE { nonContiguousUL-RA-WithinCC-Info-r10ENUMERATED{supported}OPTIONAL }Positioning in LTE
The possibility to determine the position of a wireless device has enabled application developers and wireless network operators to provide location based, and location aware, services. Examples of those are guiding systems, shopping assistance, friend finder, presence services, community and communication services and other information services giving the mobile user information about their surroundings.
The three key network elements in an LTE positioning architecture are the Location Services (LCS) Client, the LCS target and the LCS Server. The LCS Server is a physical or logical entity managing positioning for a LCS target device by collecting measurements and other location information, assisting the terminal in measurements when necessary, and estimating the LCS target location. A LCS Client is a software and/or hardware entity that interacts with a LCS Server for the purpose of obtaining location information for one or more LCS targets, i.e. the entities being positioned. LCS Clients may reside in a network node, external node, Public-Safety Answering Point (PSAP), user equipment, radio base station, etc., and they may also reside in the LCS targets themselves. An LCS Client, e.g., an external LCS Client, sends a request to LCS Server, e.g., positioning node, to obtain location information, and LCS Server processes and serves the received requests and sends the positioning result and optionally a velocity estimate to the LCS Client.
Position calculation can be conducted, for example, by a positioning server, e.g. Evolved Serving Mobile Location Centre (E-SMLC) or Service Location Protocol (SLP) in LTE or UE. The latter corresponds to the UE-based positioning mode, whilst the former may be network-based positioning, calculation in a network node based on measurements collected from network nodes such as Location Measurement Units (LMU) or eNodeBs, or UE-assisted positioning, calculation is in a positioning network node based on measurements received from the user equipment.
FIG. 2 illustrates the Uplink-Time Difference of Arrival (UTDOA) architecture being currently discussed in 3GPP. Although UL measurements may in principle be performed by any radio network node, e.g., eNodeB, UL positioning architecture may include specific UL measurement units, e.g., LMUs, which e.g. may be logical and/or physical nodes, may be integrated with radio base stations or sharing some of the software or hardware equipment with radio base stations or may be completely standalone nodes with own equipment (including antennas). The architecture is not finalized yet, but there may be communication protocols between LMU and positioning node, and there may be some enhancements for LTE Positioning Protocol annex (LPPa) or similar protocols to support UL positioning. A new interface, SLm, between the E-SMLC and LMU is being standardized for uplink positioning. The interface is terminated between a positioning server, e.g. E-SMLC, and LMU. It is used to transport SLm interface Application Protocol (SLmAP), a.k.a. LMUp, protocol, new protocol being specified for UL positioning, for which no details are yet available, messages over the E-SMLC-to-LMU interface. Several LMU deployment options are possible. For example, an LMU may be a standalone physical node, it may be integrated into eNodeB or it may be sharing at least some equipment such as antennas with eNodeB—these three options are illustrated in the FIG. 2.
LPPa is a protocol between eNodeB and LCS Server specified only for control-plane positioning procedures, although it still can assist user-plane positioning by querying eNodeBs for information and eNodeB measurements.
In LTE, UTDOA measurements, UL Relative Time of Arrival (RTOA), are performed on Sounding Reference Signals (SRS). To detect an SRS signal, LMU needs a number of SRS parameters to generate the SRS sequence which is to be correlated to received signals. SRS parameters would have to be provided in the assistance data transmitted by positioning node to LMU; these assistance data would be provided via SLmAP, a.k.a. LMUp in some sources. However, these parameters are generally not known to the positioning node, which needs then to obtain this information from eNodeB configuring the SRS to be transmitted by the user equipment and measured by LMU; this information would have to be provided in LPPa or similar protocol.
Positioning Result
A positioning result is a result of processing of obtained measurements, including Cell IDs, power levels, received signal strengths, etc., and it may be exchanged among nodes in one of the pre-defined formats. The signaled positioning result is represented in a pre-defined format corresponding to one of the seven Geographical Area Description (GAD) shapes.
Currently, the positioning result may be signaled between:                LCS target, e.g., UE, and LCS server, e.g. over LPP protocol,        Positioning servers, e.g., E-SMLC and SLP, over standardized or proprietary interfaces,        Positioning server and other network nodes, e.g., E-SMLC and Mobility Managing Entity (MME)/Mobile Switching Centre (MSC)/Gateway Mobile Location Centre (GMLC)/Operations & Maintenance (O&M)/Self-Organizing Network (SON)/Minimisation of Drive Tests (MDT),        Positioning node and LCS Client, e.g., between E-SMLC and PSAP or between SLP and External LCS Client or between E-SMLC and UE.        
In emergency positioning, LCS Client may reside in PSAPs.
Positioning result is often based on one or more radio measurements, of the same or different types, e.g., timing measurements such as timing advance and Round Trip Time (RTT) or power-based measurements such as received signal strength, received from measuring radio nodes, e.g., user equipment or eNodeB or LMU.
UTDOA or UL Positioning Measurements
As the name suggests, measurements for UL positioning and UTDOA are performed on UL transmissions, which may comprise, e.g., reference signal transmissions or UL physical channel transmissions.
UL RTOA is the currently standardized UTDOA timing measurement. The measurement may be performed on Sounding Reference Signals (SRS), which may be configured for periodic transmission. SRS transmissions may be triggered by any of the two trigger types:                Trigger type 0: higher layer signaling,        Trigger type 1: DCI formats 0/4/1A for FDD and TDD and DCI formats 2B/2C for TDD.        
UL positioning measurement performance may significantly degrade if the measuring node at least in some pre-scheduled measuring occasions tries to perform measurements on a signal which is not transmitted.
For high-quality UL measurements it is important that a measuring node can measure on as many as possible UL signals and signal occurrences. Since the measuring node can often be another node than the scheduling eNodeB, the measuring node may not be aware of scheduling decisions by the serving eNodeB for the transmitting user equipment.